Optical illumination device and projection display device

ABSTRACT

A conventional optical illumination device has a problem in which uneven brightness appears in an inclining direction when an illuminated region inclined with respect to an optical axis is illuminated. 
     An optical illumination device is formed by using a front optical illumination system, an eccentric lens, and a relay lens. The front optical illumination system is composed of a lamp, an elliptical-surface mirror, a UV-IR cut filter, a condenser, a first lens, and a second lens. 
     The relay lens conjugates a second light-emitting surface and a third light-emitting surface that are inclined with respect to an optical axis. 
     The eccentric lens is made eccentric with respect to an optical axis, effectively emits light, which is emitted from the second lens, to the relay lens, and inclines the second light-emitting surface in a direction in which brightness gradient appearing on the relay lens is canceled.

THIS APPLICATION IS A U.S. NATIONAL PHASE APPLICATION OF PCTINTERNATIONAL APPLICATION PCT/JP/01/08697.

TECHNICAL FIELD

The present invention relates to an optical illumination device used forilluminating an optical spatial modulation element, for example, and aprojection display device capable of projecting an optical image formedon the optical spatial modulation element through a projection lens ontoa screen.

BACKGROUND ART

Conventionally, as video equipment for a wide screen, projection displaydevices using various optical spatial modulation elements have beenknown. For example, these displays have translucent and reflectiveliquid crystal panels as optical spatial modulation elements, allow alight source to illuminate liquid crystal panels, form optical images onthe liquid crystal panels in response to video signals supplied from theoutside, and enlarge and project the optical images on screens throughprojection lenses.

When a projection display device is configured, it is important toachieve large optical output and to provide a bright projected imagewith high image quality. In order to achieve such a display, it isimportant to achieve an optical illumination system which canefficiently condense light emitted from a lamp and can evenly illuminatean optical spatial modulation element. Japanese Patent Laid-Open No.3-111806 and No. 5-346557 disclose an optical illumination device usingan optical integrator and a glass rod. Such a device forms alight-emitting surface, which is similar to an optical spatialmodulation element in shape, and forms an image of the light-emittingsurface on the optical spatial modulation element through a relay lensand so on, thereby achieving high efficiency and highly evenillumination.

Meanwhile, regarding an optical illumination system used for aprojection display device, for example, in some applications andconfigurations that include illumination on a reflective optical spatialmodulation element and projection with a shifted axis, an illuminatinglight beam is emitted in a direction having predetermined inclinationwith respect to the optical spatial modulation element. However, in thecase of oblique illumination using the above conventional opticalillumination systems, regarding an illuminating light beam formed on anemitted surface, the image-forming condition is maintained near anoptical axis but is not maintained at a position away from the opticalaxis. Hence, it is difficult to efficiently condense light on aneffective region on the emitted surface. Further, the problem is that afigure is distorted with respect to the inclining direction of theemitted surface, which results in uneven brightness.

In order to efficiently illuminate a surface inclined with respect to anoptical axis, it is necessary to realize an optical illumination systemfor satisfying an image-forming condition of an inclined object that isreferred to as a so-called shine-proof condition. Although the conditionrule provides an image-forming condition of two surfaces inclined toeach other but does not solve a problem in that a figure is distortedwith respect to an inclining direction of an emitted surface and unevenbrightness occurs. Such a problem has essentially occurred in obliqueillumination.

In response, as a configuration for repeating twice the shine-proofcondition, a method for solving the problem of oblique image-formationis disclosed. (e.g., Japanese Patent Laid-Open No. 4-27912).

FIG. 9(a) shows an example of a basic configuration of a conventionalprojection display device.

The conventional projection display device is constituted by a lamp 121,a concave mirror 122, a condenser 123, a light bulb 124, a first lens125, an intermediate image-forming surface 126, a reflection mirror 127,a second lens 128, and a screen 129.

Light emitted from the lamp 121 is condensed by the concave mirror 122,and a single beam of light is formed so as to be almost rotationallysymmetric with respect to an optical axis.

The condenser 123 illuminates the entire region of the light bulb 124 byusing the single beam of light and condenses light passing through thelight bulb 124 near an object-side focus 125 a of the first lens 125.

For example, a translucent liquid crystal panel is used as the lightbulb 124 and forms an optical image in response to a video signal.

The first lens 125 forms the intermediate image-forming surface 126using light passing through the light bulb 124. At the same time, lightcondensed through the condenser 123 passes near the focus 125 a of thefirst lens 125, so that the light is emitted from the first lens 125 assubstantially parallel light which surrounds the intermediateimage-forming surface 126.

The light bulb 124 and the intermediate image-forming surface 126 areinclined to each other with respect to the optical axis 125 b of thefirst lens 125 so as to satisfy the shine-proof condition.

The reflection mirror 127 disposed near the intermediate image-formingsurface 126, for example, uses minute reflecting surfaces 127 a that arearranged in two dimensions as enlarged in FIG. 9(b), so that thereflection mirror 127 allows light emitted from the first lens 125 toefficiently enter the second lens 128.

The second lens 128 forms an image of the intermediate image-formingsurface 126 again on the screen 129. The intermediate image-formingsurface 126 and the screen 129 are inclined to each other with respectto the optical axis 128 b of the second lens 128 so as to satisfy theshine-proof condition.

According to the above configuration, figure distortion appearing on thefirst lens 125 can cancel figure distortion appearing on the second lens126. Thus, on the screen 129, it is possible to form an image conjugatedto an optical image on the light bulb 123 without distortion. Moreover,since a beam of light emitted from the first lens 125 is substantiallyparallel light, there brings an advantage in that it is possible toreduce loss of light in an optical path from the first lens 125 to thesecond lens 128.

The projection display device of FIG. 9(a) solves figure distortioncaused by inclined image formation and brightness gradient caused by thedistortion, and efficiently guides light emitted from the lamp to thescreen, so that a bright projected image is obtained without distortion.Therefore, when the above configuration is applied to an opticalillumination system, it is possible to efficiently illuminate an opticalspatial modulation element inclined with respect to an optical axis.However, the following problem arises.

To be specific, when the shine-proof condition is repeated twiceregarding oblique image formation, the optical axes of the first lensand the second lens are largely refracted. Hence, a means of bending anoptical path is necessary. In FIG. 9(b), a minute reflection mirrorarray having minute reflection mirrors aligned in two dimensions isdisposed near the intermediate image-forming surface so as to form theabove means. However, since the intermediate image-forming surface has aconjugating relationship with the screen, images of edges and the likeof the minute reflection mirrors are formed on the screen.

Namely, in the conventional optical illumination device or projectiondisplay device, a problem (first problem) arises in which images ofedges and the like of the minute reflection mirrors of the optical pathbending means are formed on the screen.

Secondly, since light converged by the condenser illuminates the lightbulb in the configuration of FIG. 9(a), brightness on the light bulb,which is inclined with respect to an optical axis of a light source, hasasymmetric distribution with respect to the optical axis. Thedistribution of brightness on the light bulb is substantially reproducedon the screen by the effect of the above twice image formation, so thatan image having brightness distribution asymmetric with respect to theoptical axis is formed on the screen.

Namely, in the conventional optical illumination device or projectiondisplay device, a problem (second problem) arises in which an imagehaving brightness distribution asymmetric with respect to the opticalaxis is formed on the screen.

DISCLOSURE OF THE INVENTION

In view of the above-mentioned first problem, the present invention hasas its object the provision of an optical illumination device and aprojection display device, by which images of edges and the like ofminute reflection mirrors of an optical path bending means are notformed on the screen.

Further, in view of the above-mentioned second problem, the presentinvention has as its object the provision of an optical illuminationdevice and a projection display device, by which an image havingbrightness distribution asymmetric with respect to an optical axis isnot formed on a screen.

To solve the above-described problems, one aspect of the presentinvention is an optical illumination device of illuminating anilluminated region inclined with respect to an optical axis, comprising:

a light source,

a front optical illumination system of condensing light emitted fromsaid light source,

a light transmitting element inputted with said condensed light beam,for forming a first light-emitting surface; and

a relay optical system for forming a second light-emitting surface onsaid illuminated region using light passing through said firstlight-emitting surface, wherein

said relay optical system substantially conjugates said firstlight-emitting surface and said second light-emitting surface to eachother, said light-emitting surfaces being inclined with respect to anoptical axis of said relay optical system, and

said light transmitting element corrects a traveling direction of saidincident light beams to form said first light-emitting surface such thatan outgoing light beam is effectively incident on said relay opticalsystem, and said light transmitting element forms said firstlight-emitting surface such that said first light-emitting surface has abrightness gradient in a direction in which brightness gradientappearing in said relay optical system is canceled.

Another aspect of the present invention is the optical illuminationdevice according to the 1st invention, wherein said front opticalillumination system includes an optical integrator element for allowingsaid condensed light beam to have substantially even brightnessdistribution.

Still another aspect of the present invention is the opticalillumination device according to the 2nd invention, wherein said opticalintegrator element is composed of a first lens array and a second lensarray.

Yet still another aspect of the present invention is the opticalillumination device according to the 1st invention, wherein saidilluminating transmitting element is any one of an eccentric lens, adouble-convex lens, a graded index lens, a plastic aspherical lens, aFresnel lens, and a prism element that are made eccentric with respectto an optical axis of said front optical illumination system.

Still yet another aspect of the present invention is the opticalillumination device, wherein said eccentric lens has an asphericalsurface.

A further aspect of the present invention is the optical illuminationdevice, comprising an irradiation angle correcting element near an entryside of said illuminated region.

A still further aspect of the present invention is an opticalillumination device of luminating an illuminated region inclined withrespect to an optical axis, comprising:

a light source,

a light-condensing optical system which forms a single light beam bycondensing light emitted from said light source to form a firstlight-emitting surface substantially intersecting said optical axis,

a first relay optical system of forming a second light-emitting surfaceusing light passing through said first light-emitting surface, and

a second relay optical system of forming a third light-emitting surfaceon said illuminated region using light passing through said secondlight-emitting surface, wherein

said first relay optical system substantially conjugates said firstlight-emitting surface and said second light-emitting surface to eachother, said light-emitting surfaces being inclined with respect to anoptical axis of said first relay optical system,

said second relay optical system substantially conjugates said secondlight-emitting surface and said third light-emitting surface to eachother, said light-emitting surfaces being inclined with respect to anoptical axis of said second relay optical system, and

said first relay optical system provides to said first light-emittingsurface a brightness gradient in a direction in which brightnessgradient appearing on said second relay optical system is canceled, andforms said second light-emitting surface.

A yet further aspect to the present invention is the opticalillumination device, comprising optical bending means of bending anoptical path near said first light-emitting surface or said secondlight-emitting surface.

A still yet further aspect of the present invention is the opticalillumination device, wherein said optical path bending means is any oneof an eccentric lens, a double-convex lens, a graded index lens, aplastic aspherical lens, a Fresnel lens, and a prism element that aremade eccentric with respect to an optical axis of a light-condensingoptical system for forming said first light-emitting surface or anoptical axis of said second relay optical system.

An additional aspect of the present invention is the opticalillumination device, wherein said eccentric lens has an asphericalsurface.

A still additional aspect of the present invention is the opticalillumination device, comprising an irradiation angle correcting elementnear an entry side of said illuminated region.

A yet additional aspect of the present invention is a projection displaydevice, comprising:

said optical illumination device,

a space modulator of forming an optical image in response to a videosignal disposed substantially at the same position as said secondlight-emitting surface, and

a projection lens of projecting an optical image of said spacemodulator.

A still yet additional aspect of the present invention is a projectiondisplay device, comprising:

said optical illumination device,

a space modulator of forming an optical image in response to a videosignal disposed substantially at the same position as said thirdlight-emitting surface, and

a projection lens of projecting an optical image of said spacemodulator.

A supplementary aspect of the present invention is a projection displaydevice, comprising:

said optical illumination device

a space modulator of forming an optical image in response to a videosignal disposed substantially at the same position as said firstlight-emitting surface, wherein

said first relay lens system and said second relay lens system projectan optical image of said space modulator on a screen disposed on saidilluminated region.

A still supplementary aspect of the present invention is the projectiondisplay device, comprising a rotating color wheel having a color wheellike a disk near said first light-emitting surface to selectivelytransmit light of red, green, and blue, and

said optical spatial modulation element is subjected to color sequentialdriving.

A yet supplementary aspect of the present invention is the projectiondisplay device, comprising a rotating color wheel having a color wheellike a disk near said second light-emitting surface to selectivelytransmit light of red, green, and blue, and

said optical spatial modulation element is subjected to color sequentialdriving.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing an optical illumination deviceaccording to Embodiment 1 of the present invention;

FIG. 2 is an optical path diagram showing the effect of an eccentriclens shown in FIG. 1;

FIG. 3 is an optical path diagram showing the effect of a relay lensshown in FIG. 1;

FIG. 4(a) is a schematic diagram showing an optical illumination deviceaccording to Embodiment 2 of the present invention;

FIG. 4(b) is an enlarged sectional view showing a Fresnel lens used inthe optical illumination device according to Embodiment 2 of the presentinvention;

FIG. 5 is a schematic diagram showing an optical illumination deviceaccording to Embodiment 3 of the present invention;

FIG. 6 is a schematic diagram showing an optical illumination deviceaccording to Embodiment 4 of the present invention;

FIG. 7 is a schematic diagram showing a projection display deviceaccording to Embodiment 5 of the present invention;

FIG. 8 is a schematic diagram showing a projection display deviceaccording to Embodiment 6 of the present invention;

FIG. 9(a) is a schematic diagram showing an example of the configurationof a conventional projection display device; and

FIG. 9(b) is a schematic enlarged diagram showing the configuration ofminute reflection mirrors.

DESCRIPTION OF THE SYMBOLS

light source 1, 41, 61

front optical illumination system 7, 67

light transmitting element 9, 69

first light-emitting surface 8, 45, 68

second light-emitting surface 10, 48, 70

third light-emitting surface 12, 50, 72

relay optical system 11, 71

illuminated region 13, 51, 73

light-condensing optical system 42

first relay optical system 46

second relay optical system 49

optical spatial modulation element 92, 102

projection lens 93, 103

screen 94, 104

BEST MODE FOR CARRYING OUT THE INVENTION

Hereunder embodiments of the present invention will be described inaccordance with the accompanied drawings.

(Embodiment 1)

First, Embodiment 1 will be discussed below.

FIG. 1 is a diagram showing the configuration of an optical illuminationdevice according to an embodiment of the present invention.

The optical illumination device of the present embodiment is constitutedby a lamp 1 serving as a light source, an elliptical-surface mirror 2, aUV-IR cut filter 3, a condenser 4, a first lens 5, a second lens 6, afirst light-emitting surface 8, an eccentric lens 9 serving as a lighttransmitting element, a second light-emitting surface 10, a relay lens11 serving as a relay optical system, a third light-emitting surface 12,and an illuminated region 13. An optical system from the lamp 1 to thesecond lens 6 forms a front optical illumination system 7.

Next, the operation of the above embodiment will be discussed.

The front optical illumination system 7 efficiently condenses lightemitted from the lamp 1 and forms the first light emitting surface 8 inan arbitrary shape. To be specific, light emitted from the lamp 1, whichis disposed near a first focus F1 of the elliptical-surface mirror 2, isreflected on the elliptical-surface mirror 2. After ultraviolet andinfrared components are removed by the UV-IR cut filter 3, the light iscondensed near a second focus F2 of the elliptical-surface mirror 2.

The condenser 4 is disposed such that the focal position substantiallyconforms to the second focus F2 of the elliptical-surface mirror 2, andthe condenser 4 emits light passing through the second focus F2 of theconcave mirror 2 as light traveling substantially in parallel with theoptical axis 14.

The first lens 5 condenses incident parallel light on the second lens 6,and then the second lens 6 forms the first light-emitting surface 8which is substantially conjugated to a main surface 5 a of the firstlens 5. As shown in FIG. 1, the first light-emitting surface 8 is formedso as to intersect the optical axis 14. Therefore, when an opening ofthe first lens 5 is set suitably, the first light-emitting surface 8 canbe formed in a desired shape. The brightness distribution of the firstlight-emitting surface 8 is substantially equal to that of the mainsurface 5 a of the first lens 5 and is substantially symmetric withrespect to the optical axis 14.

Here, although the present embodiment described that the firstlight-emitting surface 8 intersects the optical axis 14, the presentembodiment is not limited to the above configuration. The firstlight-emitting surface 8 does not always need to intersect the opticalaxis 14.

Besides, although the present embodiment described that the brightnessdistribution of the first light-emitting surface 8 is substantiallysymmetric with respect to the optical axis 14, the present embodiment isnot limited to the above configuration. The brightness distribution ofthe first light-emitting surface 8 may be asymmetric with respect to theoptical axis 14.

The eccentric lens 9, which is eccentric to the optical axis 14 of thesecond lens 6, is disposed near the entry side of the firstlight-emitting surface 8. The eccentric lens 9 suitably refracts lightemitted from the second lens 6 and effectively guides the light to therelay lens 11. At the same time, brightness gradient for cancelingbrightness gradient appearing on the relay lens 11 is provided on thefirst light-emitting surface 8, and the second light-emitting surface 10is formed so as to be inclined with respect to an optical axis 15 of therelay lens 11. The relay lens 11 forms the third light-emitting surface12 which is inclined in an opposite direction from the second lightemitting surface 10 with respect to the optical axis 15, using lightpassing through the second light-emitting surface 10, and the relay lens11 effectively illuminates the illuminated region 13. The brightnessdistribution on the illuminated region 13 is substantially equivalent tothe first light-emitting surface 8, that is, the main surface 5 a of thefirst lens 5, and the distribution is substantially symmetric to theoptical axis.

Referring to FIGS. 2 and 3, the following will discuss the specificaction and effect of the above-mentioned configuration.

FIG. 2 is an optical path diagram for explaining the action of theeccentric lens 9. The eccentric lens 9 is an aspherical glass lens,which has an aspherical surface on the entry side of a light ray and hasa plane on the emitting side. The eccentric lens 9 effectively emitslight, which is emitted from the second lens 6, to the relay lens 11,and forms the second light-emitting surface 10 which is different fromthe first light-emitting surface 7 in brightness distribution.

To be specific, an optical axis 21 of the eccentric lens 9 issubstantially in parallel with the optical axis 15 of the relay lens 11and is suitably eccentric with respect to the optical axis 14 so as topass by a main point 6 a of the second lens 6. Therefore, light whichpasses through the main point 6 a of the second lens 6 and is emitted tothe eccentric lens 9 is emitted as light traveling substantially inparallel with the optical axis 15 of the relay lens 11. Thus, lightpassing through the second lens can be effectively emitted to the relaylens.

The eccentric lens 9 provides brightness gradient to the firstlight-emitting surface 8 formed on the optical axis 14 of the secondlens 6, and forms the second light-emitting surface 10 on a differentposition. The second light-emitting surface 10 is disposed withpredetermined inclination with respect to the optical axis 15 of therelay lens 11 and has distribution different from brightnessdistribution on the first light-emitting surface 8, that is, the mainsurface 5 a of the first lens 5.

For simpler explanation of a difference in brightness distribution, aparallel light beam 20 emitted to the first lens 5 is divided at equalintervals, and divided light rays are referred to as L1, L2, L3, L4, andL5. The light ray L3 corresponds to the optical axis 14 of the secondlens 6. Further, the intervals of the divided light rays are referred toas S1, S2, S3, and S4. The light rays on the main surface 5 a have equalintervals of S1=S2=S3=S4.

The light ray L1 traveling through the main surface 5 a of the firstlens 5 passes through the main point 6 a of the second lens 6 and isrefracted in the eccentric lens 9. And then, the light ray L1 travelssubstantially in parallel with the optical axis 15 of the relay lens 11and reaches a point P1 on the second light-emitting surface 10. Thelight rays L2, L3, L4, and L5 similarly travel substantially in parallelwith the optical axis 15 of the relay lens 11 and reach points P2, P3,P4, and P5 on the second light-emitting surface 10.

Here, when the light rays L1, L2, L3, L4, and L5 on the secondlight-emitting surface 10 have intervals of S1′, S2′, S3′, and S4′,S4′>S3′>S2′>S1′ is obtained. A light ray included in S1 on the mainsurface 5 a is included in S1′ on the second light-emitting surface 10.Similarly, light rays included in S2, S3, and S4 on the main surface 5 aare included in S2′, S3′, and S4′ on the second light-emitting surface10. Therefore, it is understood that the eccentric lens 9 inclinesdistribution of light beam density on the main surface 5 a and forms thesecond light-emitting surface 10 having brightness distributionasymmetric with respect to the optical axis 15.

FIG. 3 is an optical path diagram for explaining the action of the relaylens 11.

The relay lens 11 forms the third light-emitting surface 12, which issubstantially conjugated to the second light-emitting surface 10, nearthe illuminated region 13. At this moment, the second light-emittingsurface 10 and the third light-emitting surface 12 are each inclinedwith respect to the optical axis 15 of the relay lens 11.

The above relationship will be discussed in geometrical optics. Thesecond light-emitting surface 10 and the third light-emitting surface 12are disposed at image-forming positions A1 and A2 of the relay lens 11,and an extended line 31 of the second light-emitting surface 10 and anextended line 32 of the third light-emitting surface 12 pass through amain point 11 a of the relay lens 11 and intersect each other on a pointO on a line 33 perpendicular to the optical axis 15. Such a positionalrelationship is satisfied, so that an image of the second light-emittingsurface 10, which is inclined with respect to the optical axis 15, isformed on the third light-emitting surface 12. Such a relationship isreferred to as “shine-proof relationship rule” and provides animage-forming condition required for an inclined object.

Next, the following will describe how brightness distribution on thesecond light-emitting surface 10 is changed on the third light-emittingsurface 12.

Light which passes through the main point 11 a of the relay lens 11 fromthe point P1 and reaches the third light-emitting surface 12 is referredto as L1′. Similarly, light which passes through the main point 11 a ofthe relay lens 11 from the points P2, P3, P4, and P5 and reaches thethird light-emitting surface 12 is respectively referred to as L2′, L3′,L4′, and L5′. As shown in FIG. 2, the intervals of the points areS4′>S3′>S2′>S1′. Meanwhile, when the intervals of the light rays on thethird light-emitting surface 12 are referred to as S1″, S2″, S3″, andS4″, S1″=S2″=S3″=S4″ is obtained. This means that the thirdlight-emitting surface 12 is different from the second light-emittingsurface 10 in brightness distribution. At the same time, by providingbrightness distribution to the second light-emitting surface 10 so as tocancel brightness gradient appearing on the relay lens 11, even when theilluminated region 13 is diagonally illuminated, it is possible toobtain brightness distribution substantially symmetric with respect tothe optical axis 15.

In order to achieve the above brightness distribution, a focal length ofthe eccentric lens 9 is ideally set such that the focal positionsubstantially conforms to the main point 6 a of the second lens 6.Further, an eccentric quantity of the eccentric lens 9 is set such thatthe optical axis 21 is substantially in parallel with the optical axis15 of the relay lens 11.

According to the above configuration, the eccentric lens 9 inclines thebrightness distribution of the first light-emitting surface 8 formed bythe front optical illumination system 7, and the inclination is set soas to substantially cancel brightness gradient appearing on the relaylens 11. Thus, the illuminated region 13 inclined with respect to theoptical axis 15 of the relay lens 11 can be substantially equal inbrightness distribution to the first light-emitting surface 8 formed bythe front optical illumination system 7. For example, since the frontoptical illumination system 7 forms the first light-emitting surface 8with uniform brightness, the brightness distribution of the illuminatedregion 13 can be substantially uniform.

Moreover, even when the eccentric lens 9 is disposed near the secondlight-emitting surface 10, an unnecessary shadow and moir fringes do notappear on the illuminated region 13.

Here, the second light-emitting surface of the present embodiment is anexample of the first light-emitting surface of the present invention,and the third light-emitting surface of the present embodiment is anexample of the second light-emitting surface of the present invention.

Besides, the front optical illumination system of the present inventionis not limited to the front optical illumination system 7 configured asshown in FIG. 1 of the present embodiment. In short, the front opticalillumination system of the present invention only needs to condenselight emitted from the lamp and form a predetermined light-emittingsurface.

Further, the first light-emitting surface of the present invention isnot limited to a surface which intersects the optical axis 14 like thefirst light-emitting surface 10 of the present embodiment. Thus, thefirst light-emitting surface does not always need to intersect theoptical axis 14. Moreover, brightness distribution does not need to besymmetric with respect to the optical axis 14, so that brightnessdistribution may be asymmetric with respect to the optical axis 14. Inshort, the same effect can be obtained as long as the eccentric lens isset so as to satisfy the above-mentioned action.

Furthermore, the light transmitting element of the present invention isnot limited to a lens whose shape and eccentric quantity satisfy theabove-mentioned conditions like the eccentric lens 9 of the presentembodiment. In short, the light transmitting element of the presentinvention only needs to have the function of refracting incident lightto form the second light-emitting surface which cancels brightnessgradient appearing on the relay lens. Moreover, the light transmittingelement of the present invention is not limited to an element fortransforming emitted light to parallel light like the eccentric lens ofthe present embodiment, so that the element may not transform emittedlight into parallel light. In short, the light transmitting element ofthe present invention only needs to provide desired brightness gradientto the second light-emitting surface, reduce the expansion of lightemitted from the second lens, and effectively emit the light into therelay lens.

Also, the light transmitting element of the present invention is notlimited to the eccentric lens 9 of the present embodiment, so that adouble-convex lens, a graded index lens, a plastic aspherical lens, aFresnel lens, and so on are also applicable. Besides, a prism elementand the like can be used in some cases.

Additionally, the main surface 5 a of the first lens 5 and the secondlight-emitting surface 10 do not always need to be conjugated with eachother. For example, a field stop may be disposed on the emitting side ofthe eccentric lens to form the second light-emitting surface.

Further, the relay optical system of the present invention is notlimited to the relay lens 11 of the present embodiment. A plurality oflenses can be also used. In short, the relay optical system of thepresent invention only needs to substantially conjugate the secondlight-emitting surface and the third light-emitting surface.

Moreover, the second light-emitting surface 10 of the present embodimentis inclined with respect to the optical axis of the relay lens 11. Thesecond light-emitting surface 10 is an example of a relay lens forsufficiently correcting aberration. For example, when a relay lens witha large field curvature is used, a most suitable image-forming surfaceof the relay lens is set as the second light-emitting surface accordingto aberration. In some cases, the second light-emitting surface may beperpendicular to the optical axis.

As described above, according to the configuration of FIG. 1, with theeccentric lens, it is possible to provide an optical illumination devicefor reducing figure distortion and uneven brightness that have beenproblems of oblique illumination, with small brightness gradient withrespect to an inclining direction of the illuminated region.

(Embodiment 2)

Next, Embodiment 2 will be discussed below.

FIG. 4(a) is a diagram showing the configuration of an opticalillumination device according to an embodiment of the present invention.

The optical illumination device of the present embodiment is constitutedby a lamp 41 serving as a light source, a parabolic mirror 42 serving asa light-condensing optical system, a UV-IR cut filter 43, a firstFresnel lens 44 serving as a first optical path bending element, a firstlight-emitting surface 45, a first relay lens 46 serving as a firstrelay lens system, a second Fresnel lens 47 serving as a second opticalpath bending element, a second light-emitting surface 48, a second relaylens 49 serving as a second relay lens system, a third light-emittingsurface 50, and an illuminated region 51.

Light emitted from the lamp 41 is condensed through the parabolic mirror42, and ultraviolet and infrared components are removed by the UV-IR cutfilter 43. Parallel light emitted into the first Fresnel lens iscondensed to form the first light-emitting surface 45.

The first relay lens 46 conjugates the first light-emitting surface 45and the second light-emitting surface 47 to each other that are inclinedwith respect to an optical axis 53. To be specific, the firstlight-emitting surface 45 and the second light-emitting surface 47 aredisposed at image-forming positions B1 and B2 of the first relay lens46, and an extended line 55 of the first light-emitting surface 45 andan extended line 57 of the second light-emitting surface 48 intersect ona point Q on a line 56 which passes through a main point 46 a of thefirst relay lens 46 and is perpendicular to the optical axis 53.

The second relay lens 49 conjugates the second light-emitting surface 48and the third light-emitting surface 50 to each other that are inclinedwith respect to an optical axis 54. To be specific, the secondlight-emitting surface 48 and the third light-emitting surface 50 arerespectively disposed at image-forming positions C1 and C2 of the secondrelay lens 49, and the extended line 57 of the second light-emittingsurface 48 and an extended line 59 of the third light-emitting surface50 intersect on the point Q on a line 58 which passes through a mainpoint 49 a of the second relay lens 49 and is perpendicular to theoptical axis 54.

Here, although FIG. 4(a) shows an example in which the extended line 56and the extended line 58 intersect on the same point Q1, the lines donot always need to intersect on the point Q.

The first Fresnel lens 44 condenses parallel light, which is emittedfrom the parabolic mirror 42, at the main point 46 a of the first relaylens 46 as shown in an enlarged sectional view of FIG. 4(b). Thus, thefirst Fresnel lens 44 is eccentric with respect to an optical axis 52 ofthe parabolic mirror 42. To be specific, the first Fresnel lens 44 iseccentric such that an optical axis 44 a of the first Fresnel lens 44 issubstantially in parallel with the optical axis 52 of the parabolicmirror 42 and passes through the main point 46 a of the first relay lens46.

The second Fresnel lens 47 is used for effectively emitting light fromthe first relay lens 46 to the second relay lens 49. To be specific, thesecond Fresnel lens 47 is eccentric such that a focal position on theentry side is disposed around the main point 46 a of the first relaylens 46 and a focal position on the emitting side is disposed around themain point 49 a of the second relay lens 49.

According to the above configuration, brightness gradient occurring onthe second relay lens 49 can be canceled by brightness gradientoccurring on the first relay lens 46. Thus, the third light-emittingsurface 50 and the first light-emitting surface 45 can be substantiallyequal in brightness distribution.

Moreover, even when an eccentric lens 9 is disposed around a secondlight-emitting surface 48, an unnecessary shadow and moir fringes do notappear on an illuminated region 51.

Besides, an optical path bending means of the present invention is notlimited to means whose shape and eccentric quantity satisfy theabove-mentioned conditions, like the first Fresnel lens 44 and thesecond Fresnel lens 47 of the present embodiment. In short, the opticalpath bending means of the present invention only needs to have thefunction of refracting incident light to form the second light-emittingsurface for substantially cancelling brightness gradient occurring onthe second relay lens. Further, the optical path bending means of thepresent invention is not limited to a means of transforming emittedlight to parallel light like the first Fresnel lens 44 and the secondFresnel lens 47 of the present embodiment, so that it is not alwaysnecessary to transform emitted light to parallel light. In short, theoptical path bending means of the present embodiment only needs toprovide desired brightness gradient to the second light-emittingsurface, reduce the expansion of light emitted from the second lens, andeffectively emit the light into the relay lens.

Moreover, the optical path bending means of the present invention is notlimited to the first Fresnel lens 44 and the second Fresnel lens 47 ofthe present embodiment. A double-convex lens, a graded index lens, or aplastic aspherical lens may be used for the eccentric lens. A prismelement or the like is also applicable in some cases.

Additionally, the first relay optical system of the present invention isnot limited to the first relay lens 46 of the present embodiment, sothat the system may be composed of a plurality of lenses. In short, thefirst relay optical system of the present invention only needs to allowthe first light-emitting surface and the second light-emitting surfaceto substantially have a conjugating relationship.

Furthermore, the second relay optical system of the present invention isnot limited to the second relay lens 49 of the present embodiment, sothat the system may be composed of a plurality of lenses. In short, thesecond relay optical system of the present invention only needs to allowthe second light-emitting surface and the third light-emitting surfaceto substantially have a conjugating relationship.

As described above, when the configuration of FIG. 4 is used, byefficiently combining two relay optical systems which satisfy ashine-proof condition, it is possible to achieve an optical illuminationdevice which can reduce figure distortion and uneven brightness havingsmall brightness gradient with respect to an inclining direction of theilluminated region, and can effectively use light emitted from the lamp.The figure distortion and uneven brightness have been problems ofoblique illumination.

(Embodiment 3)

Next, Embodiment 3 will be discussed below.

FIG. 5 is a diagram showing the configuration of an optical illuminationdevice according to an embodiment of the present invention.

The optical illumination device of the present embodiment is constitutedby a lamp 61 serving as a light source, a parabolic mirror 62, a UV-IRcut filter 63, a first lens array 64, a second lens array 65, anauxiliary lens 66, a first light-emitting surface 68, an eccentric lens69 serving as a light transmitting element, a second light-emittingsurface 70, a relay lens 71 serving as a relay optical system, a thirdlight-emitting surface 72, and an illuminated region 73. An opticalsystem from the lamp 61 to the auxiliary lens 66 forms a front opticalillumination system 67.

Next, the operation of the above embodiment will be discussed below.

Light emitted from the lamp 61 is reflected on the parabolic mirror 62and is transformed into light traveling substantially in parallel withan optical axis 75. The UV-IR cut filter 63 removes ultraviolet andinfrared components from light emitted from the parabolic mirror 62, andthe light is emitted to the first lens array 64.

The first lens array 64 has first lenses 64 a arranged in twodimensions. An incident light beams is divided into a plurality ofminute light beams, and each of the minute light beams is condensed onthe second lens array 65. The second lens array 65 has second lenses 65a, which are paired with the first lenses 64, arranged in twodimensions. A minute light beam emitted to the corresponding first lens64 a is expanded or reduced to form the first light-emitting surface 68in a superimposing form. A plurality of minute light beams withrelatively small unevenness in brightness and color is superimposed, sothat the first light-emitting surface 68 is quite even in brightnessdistribution.

The auxiliary lens 66 is used for superimposing light, which has passedthrough the second lens 65 a, on the first light-emitting surface 68.

With the same function as that of Embodiment 1, the eccentric lens 69forms the second light-emitting surface 70, which provides brightness ina direction in which brightness gradient occurring on the relay lens 71is canceled, to the brightness distribution of the first light-emittingsurface 68. The second light-emitting surface 70 forms the thirdlight-emitting surface 72 near the illuminated region 73 through therelay lens 71.

The brightness distribution of the third light-emitting surface 73 isobtained by superimposing brightness distribution of the plurality offirst lenses 64 a and second lenses 65 a. Thus, the brightnessdistribution is quite even.

Besides, instead of using the auxiliary lens, the second lenses whichare suitably made eccentric may be arranged in two dimensions toconstitute the second lens array 65.

As described above, when the configuration of FIG. 5 is used, it ispossible to achieve an optical illumination device which can evenlyilluminate the illuminated region inclined with respect to the opticalaxis.

(Embodiment 4)

Next, Embodiment 4 will be discussed below.

FIG. 6 is a diagram showing the configuration of an optical illuminationdevice according to an embodiment of the present invention.

The configuration is identical to that of FIG. 5 except for anirradiation angle correcting lens 81.

The irradiation angle correcting lens 81 acts on light for forming athird light-emitting surface 72 and emits incident light as light whichtravels substantially in parallel with an optical axis 74. Therefore, aparallel light beam is emitted to an illuminated region at apredetermined angle.

The above configuration, for example, is effective for illuminating anoptical spatial modulation element with a different transmittance andreflection factor according to an angle of incidence.

Additionally, aberration caused by the irradiation angle correcting lens81 is preferably corrected by a relay lens 71.

As described above, when the configuration of FIG. 6 is used, it ispossible to achieve an optical illumination device which can evenlyilluminate an illuminated region, which is inclined with respect to anoptical axis, by using a parallel light beam having a predeterminedangle.

(Embodiment 5)

Next, Embodiment 5 will be discussed below.

FIG. 7 is a diagram showing the configuration of a projection displaydevice according to an embodiment of the present invention.

The projection display device of the present embodiment is constitutedby an optical illumination device 91, a reflective liquid crystal panel92, a projection lens 93, and a screen 94.

The optical illumination device 91 is identical to the opticalillumination device of FIG. 6. The optical illumination device 91 formsa parallel light beam with high evenness by using the effect ofEmbodiment 4 and illuminates the reflective liquid crystal panel 92. Thereflective liquid crystal panel 92 forms an optical image by modulatingand reflecting incident light in response to a video signal. The opticalimage on the reflective liquid crystal panel 92 is projected on thescreen 94 through the projection lens 93.

The projection lens 93 sufficiently corrects aberration appearing on anirradiation angle correcting lens 81, so that an optical image on thereflective liquid crystal panel 92 can be formed on the screen 94 athigh resolution.

Since the irradiation angle correcting lens 81 is disposed, it ispossible to reduce the expansion of light reflected on the reflectiveliquid crystal panel 92 and emit the light into the projection lens.Hence, the projection lens can be smaller in size.

Further, when an opening of a first lens 64 a on a first lens array 64is substantially identical in shape to an effective display region of aliquid crystal panel 92, it is possible to reduce unnecessary lightwhich illuminates a part other than the effective display region. Thus,the contrast of a projected image can be improved.

Moreover, when a reflective optical spatial modulation element isilluminated, a plano-convex lens which has a convex surface on the sideof the optical spatial modulation element 92 can be used as theirradiation angle correcting lens 81. By doing so, it is possible toprevent unnecessary reflected light from reentering the optical spatialmodulation element 92, thereby further improving the contrast.

Additionally, in the case of color sequential display using a colorwheel or the like, on which color filters of red, green, and blue arearranged like disks, the color wheel is disposed near a secondlight-emitting surface 70. Since a parallel light beam with a smallparallel width can be formed near the second light-emitting surface 70,it is possible to reduce wavelength shift that is caused by dependenceof the color filter on an angle of incidence.

Additionally, the optical spatial modulation element of the presentinvention is not limited to the reflective liquid crystal panel 92 ofthe present embodiment. A translucent liquid crystal panel and a mirrordevice, which modulates light by using a plurality of small mirrors, arealso applicable.

Further, the projection display device can be any of a front double-bodytype and a rear integral type to obtain the effect of the presentinvention.

Besides, the same effect can be obtained when the optical illuminationdevice of FIGS. 1 and 5 is used as an optical illumination device.

As described above, when the configuration of FIG. 7 is used, it ispossible to efficiently and evenly illuminate an optical spatialmodulation element inclined with respect to an optical axis. Hence, itis possible to achieve a projection display device which can obtain abright image with high image quality.

(Embodiment 6)

Next, Embodiment 6 will be discussed below.

FIG. 8 is a diagram showing the configuration of a projection displaydevice according to an embodiment of the present invention.

The projection display device of the present embodiment is constitutedby an optical illumination device 101, a reflective liquid crystal panel102, a projection lens 103, and a screen 104.

The optical illumination device 101 is identical to the opticalillumination device of FIG. 4. The reflective liquid crystal panel 102is illuminated by a parallel light beam which is formed by the opticalillumination device 101 and without brightness gradient. An opticalimage formed on the reflective liquid crystal panel 102 is projected onthe screen 104 through the projection lens 103.

The projection lens 103 has a sufficiently large image circle and canperform projection with a shifted axis. Thus, oblique projection ispossible without distortion on the screen 104.

As described above, when the configuration of FIG. 8 is used, it ispossible to efficiently and evenly illuminate the optical spatialmodulation element 102 inclined with respect to the optical axis. Thus,it is possible to achieve a projection display device which can obtain abright image with high image quality.

Additionally, by providing a translucent liquid crystal panelsubstantially at the same position as the first light-emitting surface45 of the optical illumination device of Embodiment 2 shown in FIG. 4, aprojection display device is obtained. Here, the above translucentliquid crystal panel forms an optical image by modulating and passingincident light in response to a video signal. The first relay lens 46and the second relay lens 49 also act as projection lenses forprojecting an optical image formed by the liquid crystal panel on thescreen disposed on the third light-emitting surface 50.

As described above, according to the present embodiment, it is possibleto achieve an optical illumination device which can efficiently condenselight emitted from the lamp and illuminate the illuminated regionwithout brightness gradient in an inclining direction, even when anilluminated region inclined with respect to the optical axis isilluminated.

Further, it is possible to achieve a projection display device which candisplay a high-quality and bright image without uneven brightness.

Industrial Applicability

As described above, the present invention can provide an opticalillumination device and a projection display device, by which edges andso on of small reflection mirrors of an optical path bending means isnot formed on a screen.

Moreover, the present invention can provide an optical illuminationdevice and a projection display device, by which an image havingbrightness distribution asymmetric with respect to an optical axis isnot formed on a screen.

What is claimed is:
 1. An optical illumination device of illuminating anilluminated region inclined with respect to an optical axis, comprising:a light source, a front optical illumination system of condensing lightemitted from said light source, a light transmitting element inputtedwith said condensed light beam, for forming a first light-emittingsurface; and a relay optical system for forming a second light-emittingsurface on said illuminated region using light passing through saidfirst light-emitting surface, wherein said relay optical systemsubstantially conjugates said first light-emitting surface and saidsecond light-emitting surface to each other, said light-emittingsurfaces being inclined with respect to an optical axis of said relayoptical system, and said light transmitting element corrects a travelingdirection of said incident light beams to form said first light-emittingsurface such that an outgoing light beam is effectively incident on saidrelay optical system, and said light transmitting element forms saidfirst light-emitting surface such that said first light-emitting surfacehas a brightness gradient in a direction in which brightness gradientappearing in said relay optical system is canceled.
 2. The opticalillumination device according to claim 1, wherein said front opticalillumination system includes an optical integrator element for allowingsaid condensed light beam to have substantially even brightnessdistribution.
 3. The optical illumination device according to claim 2,wherein said optical integrator element is composed of a first lensarray and a second lens array.
 4. The optical illumination deviceaccording to claim 1, wherein said illuminating transmitting element isany one of an eccentric lens, a double-convex lens, a graded index lens,a plastic aspherical lens, a Fresnel lens, and a prism element that aremade eccentric with respect to an optical axis of said front opticalillumination system.
 5. The optical illumination device according toclaim 4, wherein said eccentric lens has an aspherical surface.
 6. Theoptical illumination device according to claim 1, comprising anirradiation angle correcting element near an entry side of saidilluminated region.
 7. An optical illumination device of illuminating anilluminated region inclined with respect to an optical axis, comprising:a light source, a light-condensing optical system which forms a singlelight beam by condensing light emitted from said light source to form afirst light-emitting surface substantially intersecting said opticalaxis, a first relay optical system of forming a second light-emittingsurface using light passing through said first light-emitting surface,and a second relay optical system of forming a third light-emittingsurface on said illuminated region using light passing through saidsecond light-emitting surface, wherein said first relay optical systemsubstantially conjugates said first light-emitting surface and saidsecond light-emitting surface to each other, said light-emittingsurfaces being inclined with respect to an optical axis of said firstrelay optical system, said second relay optical system substantiallyconjugates said second light-emitting surface and said thirdlight-emitting surface to each other, said light-emitting surfaces beinginclined with respect to an optical axis of said second relay opticalsystem, and said first relay optical system provides to said firstlight-emitting surface a brightness gradient in a direction in whichbrightness gradient appearing on said second relay optical system iscanceled, and forms said second light emitting surface.
 8. The opticalillumination device according to claim 7, comprising optical bendingmeans of bending an optical path near said first light-emitting surfaceor said second light-emitting surface.
 9. The optical illuminationdevice according to claim 8, wherein said optical path bending means isany one of an eccentric lens, a double-convex lens, a graded index lens,a plastic aspherical lens, a Fresnel lens, and a prism element that aremade eccentric with respect to an optical axis of a light-condensingoptical system for forming said first light-emitting surface or anoptical axis of said second relay optical system.
 10. The opticalillumination device according to claim 9, wherein said eccentric lenshas an aspherical surface.
 11. The optical illumination device accordingto claim 7, comprising an irradiation angle correcting element near anentry side of said illuminated region.
 12. A projection display device,comprising: said optical illumination device according to any one ofclaims 1 to 6, a space modulator of forming an optical image in responseto a video signal disposed substantially at the same position as saidsecond light-emitting surface, and a projection lens of projecting anoptical image of said space modulator.
 13. A projection display device,comprising: said optical illumination device according to any one ofclaims 7 to 11, a space modulator of forming an optical image inresponse to a video signal disposed substantially at the same positionas said third light-emitting surface, and a projection lens ofprojecting an optical image of said space modulator.
 14. A projectiondisplay device, comprising: said optical illumination device accordingto any one of claims 7 to 11, and a space modulator of forming anoptical image in response to a video signal disposed substantially atthe same position as said first light-emitting surface, wherein saidfirst relay lens system and said second relay lens system project anoptical image of said space modulator on a screen disposed on saidilluminated region.
 15. The projection display device according to claim12, comprising a rotating color wheel having a color wheel like a disknear said first light-emitting surface to selectively transmit light ofred, green, and blue, and said optical spatial modulation element issubjected to color sequential driving.
 16. The projection display deviceaccording to claim 13, comprising a rotating color wheel having a colorwheel like a disk near said second light-emitting surface to selectivelytransmit light of red, green, and blue, and said optical spatialmodulation element is subjected to color sequential driving.